1. Technical Field
The invention relates to a device for collecting alkaline liquor that overflows from an electrolytic cell and for concurrently interrupting electrical current flow from the cell in such liquor, and, particularly, to such a device intended for use with chlor-alkali cells.
2. Background Art
Chlor-alkali electrolytic cells are typically operated in lines, in which many cells are connected electrically in series. The chlorine and hydrogen gas and weak caustic liquor (aqueous sodium hydroxide) produced by the individual cells are collected and passed into headers, through which the gaseous and aqueous products of a cell line are directed to respective storage areas, further treatment, or the like.
Weak cell liquor produced in the chlor-alkali cell is typically a hot (.about.90.degree. C.) caustic solution containing about 12-13 wt. % NaOH and 15 wt. % NaCl, and it is normally withdrawn by gravity overflow through a pipe (sometimes called a "perk" pipe) in the side of the cell container. The amount of cell liquor that overflows is dependent on the rate at which brine is fed to the chlor-alkali cell, which is a function of the size and general operating characteristics of the cell.
Because the cell liquor in the overflow pipe is in direct contact with the aqueous solution in the catholyte compartment of the cell, it is desirable to break the continuity of the overflow liquor stream to prevent a flow of electrical current from leaving the cell.
Current interruption is generally accomplished in existing chlor-alkali cell operations by allowing the overflowing cell liquor to pass out of the overflow pipe, open ended or with a stream disperser attachment, and fall or drip into an open collection funnel; see J. S. Sconce, Chlorine, Krieger Publishing Co., Huntington, N.Y., 1972, Chapter 5, pp 82, 95, 99.
This procedure has serious drawbacks: exposure of the overflow liquor to the open atmosphere allows corrosive fumes from the caustic liquor to accumulate, resulting in eye and lung irritation to workers in the cell room. The open collection funnel arrangement continues to be used because it allows visual verification by the cell room operator that cell operation, i.e., weak caustic overflow, is normal.
The present invention is a simple device that collects the overflow stream of alkaline cell liquor while simultaneously interrupting current flow, all without exposure of the caustic liquor fumes to the cell room atmosphere.